Schraermeyer U
Institute für Biologie II (Zoologie), RWTH Aachen, Bundesrepublik Deutschland.
Z Naturforsch C J Biosci. 1992 May-Jun;47(5-6):453-64. doi: 10.1515/znc-1992-0621.
The distal pigment cells of Orconectes limosus contain two layers of large electron lucent vacuoles that are separated by layers of small right-angled platelets adjacent to the crystalline cones. The crystalline cones of the dioptric apparatus of this species have evaginations into the distal pigment cell cytoplasm. In photoreceptors of Orconectes limosus and Procambarus clarkii a dark pigment accumulation site was detected just distal to the basement membrane at the edges of each retina. These pigment accumulations occurred independent of the state of light adaptation. Ultrastructurally the pigment granules at this accumulation site resemble distal screening pigment granules according to their size (up to 1.2 microns in diameter) and fibrous structure. Distal screening pigment granules were also found in tube-like cell processes or extracellularly within and proximal to the retinal basement membrane, indicating pigment transport to and across the basement membrane. Proximal to the basement membrane screening pigment granules were also observed disintegrated to a gravel-like electron dense material in widely branched cells. Evidence was found that an electron dense material, probably resulting from disintegrating screening pigment granules, was incorporated in the integument of the eyestalk. Four hours after injection of gold particles into the eye stalk distal to the retina they were detected inside and proximal to the retinal basement membrane.
光滑沼虾的远端色素细胞含有两层大的电子透明液泡，它们被与晶锥相邻的小直角血小板层隔开。该物种屈光装置的晶锥向远端色素细胞细胞质内突出。在光滑沼虾和克氏原螯虾的光感受器中，在每个视网膜边缘的基底膜远端检测到一个深色色素积累部位。这些色素积累的发生与光适应状态无关。在超微结构上，这个积累部位的色素颗粒根据其大小（直径可达1.2微米）和纤维结构类似于远端屏蔽色素颗粒。在管状细胞突起中或视网膜基底膜内及近端的细胞外也发现了远端屏蔽色素颗粒，表明色素向基底膜运输并穿过基底膜。在基底膜近端，也观察到屏蔽色素颗粒在广泛分支的细胞中分解为砾石样电子致密物质。有证据表明，一种可能由分解的屏蔽色素颗粒产生的电子致密物质被纳入眼柄的外皮中。将金颗粒注入视网膜远端的眼柄4小时后，在视网膜基底膜内和近端检测到了它们。
